Device and method for evaluating damage degree of working solution to tight reservoir

Abstract

The invention relates to the technical field of unconventional oil and gas reservoir damage evaluation, and discloses a device and a method for evaluating the damage degree of a working solution to a tight reservoir. The device comprises an upstream standard chamber, a downstream standard chamber, a core holding unit, a confining pressure pump, a needle valve, a vacuum pump, a constant-flux pump, a working solution intermediate container, a formation water intermediate container, a differential pressure gauge, a confining pressure gauge and the like. Evaluation on the damage degree of liquid permeability after a core of the tight reservoir is polluted by the working solution is realized via a differential pressure time variation parameter in a liquid pressure pulse attenuation process by an unsteady-state liquid pulse method; the experimental process efficiency is high; concerned experimental parameters are few; the current low-efficiency method for testing a damage rate of the liquid permeability by a steady-state method can be replaced; effective development of an unconventional oil and gas reservoir is facilitated; and the device and the method have certain popularization prospects.

Description

technical field [0001] The invention relates to unconventional oil and gas reservoir protection technology, in particular to a device and method for evaluating the damage degree of working fluid to tight reservoir. Background technique [0002] Unconventional oil and gas mainly include shale oil and gas, coalbed methane, tight sandstone gas and other resources. Among them, my country's tight sandstone gas has entered the stage of large-scale development, and its output has accounted for one-third of the country's total natural gas output; the scale of coalbed methane development has also increased year by year. [0003] Unconventional reservoirs are characterized by low porosity, low permeability, and high content of clay minerals. Reservoirs are extremely vulnerable to damage from working fluids such as drilling fluids, completion fluids, cementing fluids, and fracturing fluids. Once the damage occurs, it will affect the Gas well productivity, so reservoir protection is on...

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Problems solved by technology

[0004] At present, domestic unconventional reservoir damage evaluation still adopts conventional reservoir evaluation technology, and conventional reservoir damage evaluation mainly adopts the People's Republic of China Oil and Gas Industry Standard (SY / T 6540-2002 Drilling Fluid Completion Fluid Damage Reservoir Laboratory Evaluation Method) The reservoir damage evaluation experiment of the working fluid is carried out, that is, the Darcy formula method, and the permeability of unconventional reservoirs is generally lower than 1×10 -3 μm 2 , when using this method, there will be the following problems: First, the seepage of liquid in low-permeability media does not satisfy the Darcy flow characteristics, and the Darcy formula is no longer suitable for the calculation of rock sample permeability

[0005] In order to solve the problem of permeability testing of low-permeability tight reservoir cores, foreign countries have developed unsteady-state permeability testing methods, such as the gas pulse method in which the flowing medium is gas, and this technology has been introduced in China; Generally, it is necessary to evaluate the permeability damage rate when the flowing medium is liquid (such as formation water), which cannot be satisfied by the gas pulse method.

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